1. Field of the Invention
This invention relates to a process for press-forming workpieces and a bolster apparatus applicable to the same. In particular, this invention relates to a process for press-forming workpieces and a bolster apparatus applicable to the same, in which the workpieces are transferred and press-formed one after another. This invention is applicable to a bolster apparatus holding forging dies.
2. Description of the Prior Art
When performing a forging press process, a bolster is mounted to a bolster mounting portion of a forging press apparatus, a rough forging die, a finish forging die and a deflashing die are then disposed in series in die holding bores of the bolster, and a transfer is further provided to the forging press apparatus independently of the bolster. In this conventional arrangement, the forging press apparatus and the transfer are operated. Rough forged products are produced by the rough forging die from a blank material, the rough forged products produced are transferred to the finish forging die by the transfer, finish forged products are then produced by the finish forging die from the rough forged products, the finish forged products produced are transferred to the deflashing die by the transfer, and the finish forged products are finally deflashed by the deflashing die.
In the above-mentioned forging press process, a base exclusively for the transfer should be provided on the floor because the transfer is provided to the forging press apparatus independently of the bolster. In addition, when changing production set-ups from one product to another product, not only the rough forging die, the finish forging die and the deflashing die but also the bolster for holding these dies should be exchanged. Further, when a production set-up has been changed and the workpiece transfer pitch has been varied, the transfer should be exchanged in addition to the above-mentioned exchanges of the forging dies and bolster. It is therefore disadvantageous in view of productivity because a process for exchanging the transfer is required as well as a process for exchanging the forging dies and the bolster.
In order to overcome the above-mentioned drawbacks, a transfer adapted to the multi-function or the multi-purpose application should be employed to make the workpieces transferable with an identical transfer even when the production set-ups have been changed. Consequently, the mechanism and function of the transfer is complicated, and the cost thereof is high.
For example, a schematic plan view of a conventional transfer is illustrated in FIG. 19. As shown in FIG. 19, the conventional transfer comprises frames 901 comprising a workpiece transfer path 900 extending in the X-direction, and a square movement mechanism 902 for intermittently transferring workpieces on the workpiece transfer path 900 in the X-direction.
The square movement mechanism 902 comprises a driving mechanism 903 disposed at one end of the X-direction, i.e., at the beginning end of the workpiece transfer, a driven mechanism 904 disposed at the other end of the X-direction, i.e., at the terminating end of the workpiece transfer, and a beam-shaped synchronizing mechanism 905 for connecting and synchronizing the driving and driven mechanisms 903 and 904. The driving mechanism 903 is provided with an X-direction driver. The beam-shaped synchronizing mechanism 905 is driven to perform a square movement along the X-direction in the upward and downward directions. The synchronizing mechanism 905 is provided with transfer claws 906 for holding workpieces. When the synchronizing mechanism 905 is driven to perform the square movement mechanism in the upward and downward directions, the workpieces held by the transfer claws 906 are intermittently transferred on the workpiece transfer path 900 one after another in the X-direction by one (1) pitch. The workpieces thus transferred are processed at processing steps disposed at every one (1) pitch.
The above-mentioned conventional transfer is provided with the square movement mechanism 902. The square movement mechanism 902 comprises the driving mechanism 903 disposed at one end of the X-direction, i.e., at the beginning end of the workpiece transfer, the driven mechanism 904 disposed at the other end of the X-direction, i.e, at the terminating end of the workpiece transfer, and the beam-shaped synchronizing mechanism 905 for synchronizing the driving and driven mechanisms 903 and 904. In the square movement mechanism 902, the synchronizing mechanism 905 is bridged in the X-direction, in which the workpieces are transferred one after another. When the number of workpiece processing steps increases, the length of the workpiece transfer path 900 increases. Accordingly, the beam-shaped synchronizing mechanism 905 should be made longer, and it is required to highly strengthen and rigidify the beam-shaped synchronizing mechanism 905 in order to prevent the beam-shaped synchronizing mechanism 905 from bending. As a result, the weight and inertia force of the beam-shaped synchronizing mechanism 905 increase. Therefore, in the above-mentioned conventional transfer, the inertia force thereof, exerted by the square movement of the beam-shaped synchronizing mechanism 905, tends to increase when the number of workpiece processing steps increases.
Further, in the above-mentioned forging press apparatus, each of the rough forging die, the finish forging die and the deflashing die is made integral. Consequently, it is not always easy to take out the products from the cavities of the dies, depending on the cavity configurations, volumes and the like of the dies.